1. Field of the Invention
The present invention relates to a bookbinding cover with an adhesive which is used for simply binding the documents produced by printing or copying at offices or homes.
2. Description of the Related art
An example of such bookbinding covers is disclosed in Japanese Patent Publication No. 61-4675 in which a back plate has an adhesive layer, and each of a front cover and a rear cover has a portion on the inside thereof which is near the back plate and to which an adhesive is applied for limiting the position of sheets of paper to be bound and for providing adhesive reinforcing.
Japanese Utility Model Laid-Open No. 59-17746 discloses the structure of a bookbinding resin sheet in which a nonwoven fabric, paper, woven fabric or the like used as a base material is impregnated with a so-called hot-melt adhesive, and an adhesive layer is also provided on the front and rear sides of the base material. The sheet formed can be used as a bookbinding sheet having a bound portion with improved strength and durability.
In Japanese Utility Model Laid-Open No. 61-50469, capsules containing a liquid adhesive are placed on tape-like base paper and are broken by employing heat and pressure in order to bind sheets of paper which form the pages of a book.
Japanese Utility Model Laid-Open No. 61-180752 discloses a design in which kerfs are provided in the hot-melt adhesive provided on the inside of a back plate in the lengthwise direction thereof so that the adhesive portion can be folded corresponding to the amount (thickness) of sheets to be bound.
Further, Japanese Patent Laid-Open No. 48-53821 discloses a cover with an adhesive.
Although all the examples of prior art disclose the arrangement and shape of an adhesive, they disclose no bonding ability of the adhesive used.
An adhesive layer in a back plate is generally required to have sufficient strength because it is repeatedly bent when the book is opened and closed.
On the other hand, hot-melt adhesives are effective in bookbinding from the viewpoints of the easiness and speed of adhesion, and hot-melt adhesives having appropriately low heat-melting temperatures are particularly effective. Namely, since hot-melt adhesives are melted by heating and solidified by cooling in order to complete bonding, they are suitable for simple bookbinding. In addition, because hot-melt adhesives having low heat-melting temperatures can be made molten with low heat energy, i.e., at relatively low heating temperatures, the heating time required for producing an adhesive state is short. Since the time required for cooling and solidification in order to complete adhesion is also relatively short, such hot-melt adhesives have useful properties.
Examples of methods employed for decreasing the heat-melting temperatures of hot-melt adhesives include a method of decreasing the molecular weight of the material used, a method of mixing a component having a low molecular weight and the like. However, all the methods bring about decreases in mechanical strength of the adhesive layers formed and thus produce results which are contrary to the necessary conditions for bookbinding in which an important factor is the flexural strength of the bonded portion in the back plate.